Swirrel is a little framework (in alpha state) which allows to annotate AWT or Swing Components instead of writing listeners. Swirrel reads the annotations and attaches the aproriate listeners automatically. All you have to do is to provide the name of the methods which should be called by the Swirrel listener.
Swirrel is a double edged sword, it can make things much easier, but you can shoot yourself in the foot (hey, a sword you can shoot with!). Please consider carefully if Swirrel is right for you and your project, especially if it contains deeply nested, complex, dynamic and/or time critical GUIs. Note that using Swirrel requires more testing, as things that caused compile time errors before cause runtime errors now. That said I must say Swirrel runs much smoother than I expected.

Swing Data Binding
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A powerful, fast, light and simple data binding framework for Java 6
Easy to use, understand and to extend to support custom ui elements
Fast and light
Support PropertyChangeSupport if you want it
Swap out your model objects for active bindings (rebind)
Unbind will remove all listeners
Supply user feedback with ease
Out-of-the-box support for JXDatePicker and Joda Time
Provides a fluent interface if that's your bag

Jspresso is an innovative framework for building rich internet applications. Jspresso dramatically reduces the development cycles needed to get your corporate application up and running while not sacrificing quality, robustness and performance. Jspresso is not just another webapp framework. Jspresso based applications offer the exact same ergonomics as desktop applications while keeping an N-tier, server-centric architecture on a java backend. Jspresso-based applications can be deployed either in Adobe's Flex, qooxdoo, WingS, ULC and Swing, all on the same codebase and without a single specific line of GUI code. And last but not least, Jspresso is free.

Griffon is a Grails like application framework for developing desktop applications in Groovy. Inspired by Grails, Griffon follows the Convention over Configuration paradigm, paired with an intuitive MVC architecture and a command line interface. Griffon also follows the spirit of the Swing Application Framework (JSR 296), it defines a simple yet powerful application life cycle and event publishing mechanism. Another interesting feature comes from the Groovy language itself: automatic property support and property binding (inspired by BeansBinding (JSR 295)), which makes creating observable beans and binding to their properties a snap! As if property binding was not enough Groovy's SwingBuilder also simplifies building multi-threaded applications, say goodbye to the ugly gray rectangle (the bane of Swing apps)!
Grails developers should feel right at home when trying out Griffon. Many of Grails' conventions and commands are shared with Griffon. Granted, Swing is not the same as HTML/GSP but Builders simplify the task of creating the UI.
Seasoned Java developers will also be able to pick up the pace quickly, as the framework relieves you of the burden of maintaining an application structure, allowing you to concentrate on getting the code right.

aTunes is a full-featured audio player and manager, developed in Java programming language, so it can be executed on different platforms: Windows, Linux and Unix-like systems, ...
Currently plays mp3, ogg, wma, wav, flac, mp4 and radio streaming, allowing users to easily edit tags, organize music and rip Audio CDs.

Overview
jPod Renderer is is the long awaited rendering implementation for AWT and SWT.
Based on the successful jPod library, this one adds a platform abstraction which allows for
* pluggable PDF image conversion from and to AWT and SWT
* pluggable PDF font handling
* platform independent PDF rendering with adapterf for AWT and SWT
This library is commercial strength and used in products like
* CABAReT Stage (free for personal use)
* Sign Live!
* PDF/A Live!

For Java developers writing GUI layouts by hand that wants simplicity, power and automatic per platform fidelity, that are dissatisfied with the current layout managers in Swing and SWT, MiGLayout solves all your layout problems. Unlike JGoodies' FormLayout and Clearthought's TableLayout - MiGLayout solves all your layouts with equal ease in a way that is easy to change and maintain. You will understand how the layout will look like when looking at the code.
MiGLayout is the most versatile and flexible Swing and SWT Layout Manager for Java, yet it is very easy to learn and use. It is using String or API type-checked constraints to format the layout. MiGLayout can produce flowing, grid based, absolute (with links), grouped and docking layouts. You will never have to switch to another layout manager ever again! MiGLayout is created to be to manually coded layouts what Matisse/GroupLayout is to IDE supported visual layouts.

Java SwingBuilder is an implementation of a Java Builder geared towards building UI interfaces using Java Swing.
Details
The main class is org.javabuilders.swing.SwingBuilder. It loads the object definition from a YAML file that is in the same package and has the same base name as the calling Java class. So, if you're building org.test.MyFrame.java it will look for org.test.MyFrame.yaml for the object build file (similar to the convention the Apache Wicket web framework uses).

Foxtrot is an easy and powerful API to use threads with the JavaTM Foundation Classes (JFC/Swing).
The Foxtrot API are based on a new concept, the Synchronous Model, that allow you to easily integrate in your Swing code time-consuming operations without incurring in "GUI-freeze" problem, typical of Swing applications.
While other solutions have been developed to solve this problem, being the SwingWorker (see also here for an update) the most known, they are all based on the Asynchronous Model which, for non-trivial Swing applications, carries several problems such as code asymmetry, bad code readability and difficult exception handling.
The Foxtrot API cleanly solves the problems that solutions based on the Asynchronous Model have, and it's simpler to use.
Your Swing code will immediately benefit of:
* code symmetry and readability
* easy exception handling
* improved mantainability

Scrinch is a stand-alone Swing application that helps managing your projects using the Scrum method. Easy to configure : not based on Web technology, no database to manage : just launch it and start working.

Lobo [download] is an open source web browser that is written completely in Java.
Lobo is being actively developed with the aim to fully support HTML 4, Javascript and CSS2. Lobo also supports direct JavaFX rendering.
The general goal of the Lobo browser effort is to produce a browser that is fast, complete, easy to extend, feature-rich and secure.

Pivot is an open-source framework for building high-quality, cross-platform applications that are deployable both via the web and to the desktop. It began as an R&D effort at VMware but has now been made available to the community as an option for developers who want to build rich internet (RIA) applications in Java.
Sample Pivot application
Pivot applications are written using a combination of Java and XML and can be run either as an applet or as a standalone (optionally offline) desktop application. While Pivot was designed to be familiar to web developers who have experience building AJAX applications using HTML, CSS, and JavaScript, it provides a much richer set of standard widgets than HTML, and allows developers to create sophisticated user experiences much more quickly and easily. Pivot will also seem familiar to Swing developers, as both Swing and Pivot are based on Java2D and employ a model-view-controller (MVC) architecture to separate component data from presentation. However, Pivot includes additional features that make building modern GUI applications much easier, including declarative UI, data binding, effects and transitions, and web services integration.